In general, a register set is used to define the operation modes of a semiconductor device, and it is provided with a mode register set (MRS) and an extended mode register set (EMRS). The MRS and the EMRS set the operation modes of a semiconductor device based on the values applied to the address pins with a mode register set command. Information about the set operation modes is substantially maintained until a semiconductor device is reprogrammed or its power is interrupted. The MRS is necessary for synchronous dynamic random access memories (SDRAM) or static random access memories (SRAM). Before a semiconductor device is in use, the MRS sets the operation modes of the semiconductor device such as burst length (BL), column address strobe (CAS), signal latency (CL), and read latency (RL).
Meanwhile, the semiconductor devices used in mobile devices, such as portable computers, PDAs, hand-held phones, and so on (hereinafter, referred to as “mobile memory chips”) are required to reduce power consumption to improve the portability of the mobile devices having such mobile memory chips therein. The mobile memory chips are also required to improve the data transfer rate to increase the operating speeds of mobile devices having such memory chips therein. To meet these demands, a low power DDR2 (LPDDR2) technology was developed to dramatically improve both the power consumption and the data transfer rate. The LPDDR2 technology can implement the data transfer rate of 800 Mbps, which is currently the highest in the industry, at an operating voltage of 1.2 V. Furthermore, since an ultra-fine 66-nano process is applied to the LPDDR2 technology, a mobile memory chip can be packaged to a size of 9 mm×12 mm.
According to the LPDDR2 technology specification, the specification defines an MRS to set a signal for the information on the internal temperature change of a semiconductor device and to store the information in a register.